1. Field of the Invention
The present invention relates to fast-rise-time, short duration microwave signal devices and more particularly to an arc-activated, passive, in-line, microwave expander for generating fast-rise-time pulses from magnetron pulses.
2. Description of the Prior Art
Fast-rise-time, high power microwave (HPM) pulses from high performance radars may be able to pass through electronic protection devices such as diode limiters before these devices turn on, thereby potentially damaging receiver front ends. The pulse leaking past a protection device may be quite short in duration and significantly high in power (10 to 100 kW). Devices like PIN diode limiters, terminal protection devices and other similar systems react differently when subjected to these fast rising pulses. Studying the spike leakage and damage threshold of these devices is necessary so that systems can be optimally protected. Consequently, there is a great need to test these electronic systems with fast-rise-time, HPM pulses in order to understand and improve their immunity.
Present devices for producing fast-rise-time, high power microwave pulses include diode switches, laser-switched semiconductors, switched waveguide cavities, and transmit-receive tubes. However, these devices have proved cumbersome and impractical. For example, a diode switch can only operate at low power levels, therefore it must be followed by expensive traveling-wave tube (TWT) amplifiers to obtain the high power levels required for testing. In contrast, a laser-switched semiconductor, which works on the principle of changing the impedance of the semiconductor using laser light, can operate in the megawatt region but requires a large and expensive laser system which must be brought into the same location as the large and expensive high power source. A switched waveguide cavity is undesirable because it requires a microwave source with high spectral purity which is much more expensive than a conventional magnetron. Lastly, although the reflected pulse used from a TR tube gives a fast rise time at high power levels, it is limited because TR tubes are narrow band devices, made only in waveguide, and work only at limited specified power levels. TR tubes also require a circulator or directional couplers, adding to the cost.
It may be appreciated that there is a great need for an easy to use device that produces a fast-rise-time, HPM pulses for testing purposes.